PKC-iota drives EGFR-TKI resistance in EGFR-mutated NSCLC by phosphorylating FASN to reprogram lipid metabolism

Background: Non-small cell lung cancer (NSCLC) remains a significant challenge to global public health issues. However, epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) resistance inevitably occurs in treating EGFR-mutant NSCLC, and the underlying metabolic mechanisms remain unclear. The objective of our study is to explore the regulatory mechanisms of the atypical protein kinase C-iota (PKC-iota) in reprogramming lipid metabolism and whether this regulation contributes to the EGFR-TKI resistance in EGFR-mutant NSCLC. Methods: We use mass spectrometry (MS) co-immunoprecipitation, proximity ligation assays and molecular docking to investigate the interaction of PKC-iota and fatty acid synthase (FASN). Subsequently, Western blot assay, MS, lipid staining, membrane fluidity assay, and membrane proteins assay were performed to investigate how PKC-iota regulated the lipid metabolism by FASN. We established four types of transiently transfected H1975 and PC9 cell lines. These models were then employed in a series of assays—including Cell Counting Kit-8 (CCK-8), flow cytometry, cell counting, and colony formation—to evaluate changes in cell proliferation and EGFR-TKIs sensitivity. Four types of stably transfected H1975 cell lines were inoculated into female BALB/c nude mice, then the tumorigenicity and osimertinib sensitivity of the cell groups were analyzed. Finally, we collected 45 tumor samples of EGFR-mutated NSCLC patients to examine the clinical significance of the PKC-iota/FASN axis. Results: We observed that PKC-iota physically interacted with FASN and stabilized the FASN protein by phosphorylating it and inhibiting its ubiquitin-proteasome degradation at the post-transcriptional level. PKC-iota enhanced short/medium-chain and unsaturated fatty acid synthesis via FASN, and the PKC-iota/FASN axis increased membrane fluidity to inhibit lipid raft-mediated EGFR endocytosis and degradation while upregulating EGFR membrane localization and promoting EGFR overactivation in NSCLC. The increased tumor growth and EGFR-TKI resistance induced by the PKC-iota/FASN axis were observed both in vivo and in vitro. Clinically, we showed that high co-expression of PKC-iota and FASN correlated with poor EGFR-TKI response in EGFR-mutated NSCLC. Conclusions: Our study elucidates a mechanism of EGFR-TKI resistance mediated by the PKC-iota/FASN axis through reprogramming lipid metabolism in EGFR-mutated NSCLC, which provides a novel therapeutic target for overcoming EGFR-TKI resistance and improving the prognosis of EGFR-mutated NSCLC patients.